Abstract: Image differencing is a widely used method in moving target detection nowadays. Since most of the work only use the absolute value of difference images and the motion of the background must be compensated, the reliability and practicality of the method are not satisfactory. A new moving target detection method that uses both the positive and negative difference images is proposed in this paper. The new method detects moving target by calculating the positive and negative difference images respectively and making use of the symmetry of amplitude, shape and motion information for a moving target area in positive and negative difference images. The detection results of aircraft tailflame sequential images are given at the end of the paper. The experiment shows that the method can improve the reliability and efficiency for the moving target detection.